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PatchSiren cyber security CVE debrief

CVE-2026-78450 Microsoft CVE debrief

CVE-2026-78450 is a high-severity vulnerability in the Reliable Multicast Transport Driver (RMCAST) that allows unauthorized attackers to execute code over a network. The vulnerability has a CVSS score of 8.1 and is considered high severity. Microsoft has provided a vendor advisory for this vulnerability. This vulnerability is a use-after-free issue, and defenders should prioritize patching, especially in environments where the affected systems are exposed to the internet or untrusted networks. The affected systems include Windows 10, Windows Server 2019, Windows Server 2022, and Windows Server 2025. It is essential to verify the inventory of affected systems and monitor for patch

Vendor
Microsoft
Product
Windows 10 Version 1809
CVSS
HIGH 8.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-16
Advisory published
2026-09-08
Advisory updated
2026-09-16

Who should care

Defenders responsible for patching and vulnerability management, especially those managing Windows systems, should be aware of this vulnerability and prioritize patching.

Why it matters

CVE-2026-78450 is a high-severity vulnerability in the Reliable Multicast Transport Driver (RMCAST) that allows unauthorized attackers to execute code over a network. Defenders should prioritize patching, especially in environments where the affected systems are exposed to the internet or untrusted networks.

  • Potential code execution over a network
  • High severity vulnerability with CVSS score of 8.1
  • Affected systems include Windows 10, Windows Server 2019, Windows Server 2022, and Windows Server 2025

Technical summary

The vulnerability is a use-after-free issue in the Reliable Multicast Transport Driver (RMCAST). The CVE record and NVD entry provide details on the vulnerability, including a CVSS score of 8.1 and a high severity rating. The affected systems include Windows 10, Windows Server 2019, Windows Server 2022, and Windows Server 2025.

Defensive priority

Defenders should prioritize patching this vulnerability, especially in environments where the affected systems are exposed to the internet or untrusted networks.

Recommended defensive actions

  • Patch affected systems, especially those exposed to the internet or untrusted networks
  • Verify inventory of affected systems
  • Monitor for potential exploitation attempts

Evidence notes

The vulnerability is described as a use-after-free issue in the Reliable Multicast Transport Driver (RMCAST). The CVE record and NVD entry provide details on the vulnerability, but the exact scope of affected systems and potential impact require further verification.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-78450 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-78450

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-78450 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-78450

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.